In a silver halide photographic material, the photographic emulsion layer and other hydrophilic colloidal layers are frequently colored for the purpose of absorbing light in a certain wavelength range.
In the case where the spectral composition of the light to be incident upon the photographic emulsion needs to be controlled, a colored layer is normally provided farther from the support than the photographic emulsion layer. Such a colored layer is called a filter layer. If a plurality of photographic emulsion layers are provided, a filter layer may be provided in between these photographic emulsion layers.
For the purpose of inhibiting image unsharpness or halation caused by the second incidence of light which has been scattered during or after the transmission by the photographic emulsion layer and reflected by the interface of the emulsion layer with the support or the surface of the light-sensitive layer opposite the emulsion layer into the photographic emulsion layer, a colored layer called an antihalation layer is normally provided between the photographic emulsion layer and the support or on the side of the support opposite the photographic emulsion layer. In the case where a plurality of photographic emulsion layers are provided, an antihalation layer may be provided between these photographic emulsion layers.
In order to inhibit the reduction in the image sharpness due to the scattering of light in a photographic emulsion layer (generally referred to as "irradiation"), the photographic emulsion layer is often colored.
These hydrophilic colloidal layers to be colored normally comprise a dye. Such a dye must meet the following requirements:
(1) To exhibit a proper spectral absorption corresponding to the purpose;
(2) To be photochemically inert (i.e., to have no adverse chemical effects on the properties of the silver halide photographic emulsion layer, e.g., sensitivity drop, regression of the latent image, fog);
(3) To be insusceptible to discoloration at the photographic processing step or elution with the processing solution or washing water, leaving no harmful coloring on the processed photographic light-sensitive material;
(4) To be nondiffusible from the dyed layer to other layers; and
(5) To exhibit an excellent ageing stability in a solution or photographic material and hence be insusceptible to discoloration.
In particular, if the colored layer is a filter layer or an antihalation layer provided on the same side of the support as the photographic emulsion layer, it is often necessary that these layers be selectively colored so that other layers are not substantially colored. Otherwise, these layers not only exert harmful spectral effects on the other layers but also lose their filter or antihalation effects. However, if the layers containing a dye come into wet contact with other hydrophilic colloidal layers, the diffusion of a part of the dye from the former layers to the latter layers often occurs. In order to inhibit such a phenomenon, many efforts have heretofore been made.
For example, a method which comprises allowing a hydrophilic polymer having an electric charge opposite in sign to the charge of a dissociated anionic dye to be present in the layer as a mordant with which the dye molecule interacts so that the dye is localized in a certain layer is disclosed in U.S. Pat. Nos. 2,548,564, 4,124,386, and 3,625,694.
Further, a method which comprises dyeing a certain layer with a water-insoluble dye solid is disclosed in JP-A-56-12639 (the term "JP-A" as used herein means an unexamined published Japanese patent application), 55-155350, 55-155351, 63-27838, and 63-197943, European Patents 15,601, 274,723, 276,566, and 299,435, U.S. Patent 4,803,150, and WO 88/04794.
Moreover, a method which comprises dyeing a certain layer with finely divided metal salt grains having a dye adsorbed thereon is disclosed in U.S. Pat. Nos. 2,719,088, 2,496,841, and 2,496,843, and JP-A-60-45237.
However, even these methods leave much to be desired. These methods are disadvantageous in that they have a low decoloring rate during development and thus cannot always decolor properly when there are alterations in various factors, e.g., expedition of processing and improvements in the composition of the processing solution or the composition of the photographic emulsion.